ASoC: Convert wm8978 to direct regmap API usage

Helps push the register cache code down out of ASoC and improves resume
times by using the more efficient regmap cache sync code.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/codecs/wm8978.h b/sound/soc/codecs/wm8978.h
index c75525b..6ae4349 100644
--- a/sound/soc/codecs/wm8978.h
+++ b/sound/soc/codecs/wm8978.h
@@ -67,6 +67,8 @@
 #define WM8978_OUT3_MIXER_CONTROL		0x38
 #define WM8978_OUT4_MIXER_CONTROL		0x39
 
+#define WM8978_MAX_REGISTER			0x39
+
 #define WM8978_CACHEREGNUM			58
 
 /* Clock divider Id's */